This argument reminds of the old RDM Melee argument where someone says "My Melee RDM can keep up with WARs and SAMs and DRGs blah blah blah." What they fail to mention is that they have 50 mil worth of gear. The point they miss is that with a similar investment of gear, the DD class wouldn't even be within sight of the Melee RDM.
A players end efficiency = Skill + Gear + Base (probably multiplied by another variable called "Circumstances", but we're going to assume this value is the same for this comparison).
Sure, a player with high Skill and/or Gear can make up the difference of the base, but if that player added his/her skill and gear to that higher base in the first place, then the end efficiency would, in turn, be higher. I think it is pretty easy to prove beyond a reasonable doubt that WHM/SCH has a higher base efficiency than WHM/RDM.